Our Zebra sport tatami have been on concrete for almost 6 years now and are fine. The sport tatami that I have experienced on padding always seems uncomfortable to me. When you step near an edge it has a tendency to create an uneveness that can stub toes, etc. I know of two people that have broken toes due to this. The sport tatami work best on a surface that absorbs shock without throwing much of it back. My next dojo will be designed that way. Hopefully we can build it in within a couple of years.